1. Field of the Invention
The present invention relates generally to illumination and signal lighting. In particular, the present invention relates to directional light sources (e.g., lamps) such as a parabolic aluminum reflector (PAR) type, metallized reflector (MR) type and the like. The present invention is specifically directed to light transforming devices that provide a precisely determined light distribution pattern, such as those used for aircraft approaches, landing and navigation.
2. Discussion of the Related Art
Most conventional light sources (incandescent, halogen, fluorescent, high discharge, high pressure, etc.) by their nature are almost omnidirectional sources in that they emit light in all directions.
For applications that require light distribution in limited angles or areas, conventional light sources are typically used in combination with reflectors that collect and direct the light generated by the source.
In applications such as precision technical lights, specifications call for complicated light distribution in both the horizontal and vertical planes. For example, the International Civil Aeronautical Organization (ICAO) requirement for threshold lighting, installed in the touch-down zone on a runway, includes the following specification: intensity minimum average 10,000 candelas in an area limited by ±5.5 degrees in the horizontal and from 1 to 10 degrees in the vertical; intensity minimum 1,000 candelas in an area limited by ±7.5 degrees in the horizontal and from 1 to 14 degrees in the vertical; and intensity minimum 500 candelas in an area limited by ±9 degrees in the horizontal and from 0 to 14 degrees in the vertical.
Fulfilling this specification using conventional light sources in combination with conventional optical designs results in illumination that exceeds the specification requirements by several times, thereby providing the user with a high power consumption system that is very inefficient (see FIG. 1).
A new generation of lighting devices is based on solid state technology. In addition to other benefits, light emitting diodes (LEDs) have higher efficiency in that they produce more light per watt and they have an extremely long life. Recent advances have taken place in the area of directional LED lamp construction.
One of the basic categories of LED lamp construction is the implementation of multiple LEDs in a cluster to combine luminous flux from multiple LEDs using primary optics integrated in the LED for directionality, in addition to so-called “side-emitting” LEDs with relatively narrow omnidirectional patterns.
The other basic category of construction of LED lamp design is based on the use of an additional optical element (a “secondary optic”) to concentrate and direct the light (e.g., the implementation of a refractive lens, using a reflector as a secondary optic, etc.).
Unfortunately, none of the current designs based on the use of LEDs in combination with conventional optics (refractive or reflective) provides high efficiency performance because almost all conventional optic designs are based on the “point source” concept with the assumption that the light source has a negligible physical size which is work for low power LEDs typically having a lighting body tens to hundreds of microns.
With the tendency of the LED technology to reach high power, the physical size of the LED chips are becoming much larger. For example, Lumelid's Luxeon Star™ 1 watt LED has a chip that is 0.5×0.5 mm and Luxeon Star™ 5 watt is 2.0×2.0 mm2. Increasing light source size with the use of conventional optics creates a sufficient aberration, resulting in large losses and low efficiency.
What is needed, therefore, to overcome these limitations found in conventional systems is the application of solid-state technology (e.g., light emitting diodes) using nonimaging optics (NIO) as a secondary optic for precision spatial light distribution.